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'Clouds' In Intake On Take Off  
User currently offlineSilverfox From United Kingdom, joined Mar 2001, 1058 posts, RR: 0
Posted (12 years 1 month 1 week 5 days 15 hours ago) and read 2020 times:

When i flew a BA 747 i was in the rear facing seat. On the take off run, as the engines spooled up the intakes had a 'cloud' form inside them. it remained for about 10-15 secs (i will check on the video) before disappearing.
What caused this? is it a normal phenomenom, or just the weather conditions at the time?
I havent checked any other intakes as i am normally behind or adjacent to them.
Any ideas etc?

8 replies: All unread, jump to last
 
User currently offlineBA From United States of America, joined May 2000, 11153 posts, RR: 59
Reply 1, posted (12 years 1 month 1 week 5 days 15 hours ago) and read 2010 times:

It's vapor being sucked inside the engine.

It has to do with the weather conditions like you said. The air must have had a lot of moisture. Otherwise known, it was very humid.

It's perfectly normal and nothing to worry about.

Regards



"Generosity is giving more than you can, and pride is taking less than you need." - Khalil Gibran
User currently offlineSilverfox From United Kingdom, joined Mar 2001, 1058 posts, RR: 0
Reply 2, posted (12 years 1 month 1 week 5 days 15 hours ago) and read 2005 times:

Not worried at all. just fascinated by it. I thought it might have something to do with weather conditions, just needed a confirm. very spectacular in my opinion.
Now we are going to get all the 'neds' looking backwards on takeoff!!


User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 3, posted (12 years 1 month 1 week 5 days 15 hours ago) and read 1996 times:

No biggie, just very humid air. You can also sometimes see it along the leading edges, the wing root, and vapor trails off the wingtips...


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Photo © Gregg Stansbery



Some non-experienced travelers freak out a bit, as they think it's "smoke"....


User currently offlineLZ-TLT From Germany, joined Apr 2001, 431 posts, RR: 0
Reply 4, posted (12 years 1 month 1 week 5 days 15 hours ago) and read 1988 times:

A common phenomenon when taking off in high humidity and/or low air temperatures.

As air is sucked into the jet intakes or passes the wing's leading edge, it has a high velocity relatively to the aircraft's parts(ie, engine intake, wing and so on). Since the high velocity produces high dynamic pressure(in means of elementary fluid mechanic), but the sum of the dynamic, static and hydrostatic pressure for a given fluid remains always constant(Bernoulli's equation) and the hydrostatic pressure of the atmosphere depends only on weight, the increase of dynamic pressure is compensated by a drop in static pressure. Lower static pressure means, the condensation threshold for dissolved water vapour sinks, so the water vapours in the air condensate and form this fascinating fog. The same happens over the wing's leading edge.

There are a lot of photos here at a.net where you can see the same thing. A breathtaking sight indeed.


User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 5, posted (12 years 1 month 1 week 5 days 15 hours ago) and read 1964 times:

Forgot to add this one earlier...


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Photo © Matsushita Masashi - aozora karugamotai -



User currently offlineBA From United States of America, joined May 2000, 11153 posts, RR: 59
Reply 6, posted (12 years 1 month 1 week 5 days 11 hours ago) and read 1893 times:

Quite fascinating what water can do.  Smile

Humid air and planes make a good combination.  Big grin

Regards



"Generosity is giving more than you can, and pride is taking less than you need." - Khalil Gibran
User currently offlineSilverfox From United Kingdom, joined Mar 2001, 1058 posts, RR: 0
Reply 7, posted (12 years 1 month 1 week 4 days 13 hours ago) and read 1793 times:

Thanks for all the info, i knew about the vortex etc, but as i said it was the first time i had seen it on engines..still get a kick on the video watching it.
Thanks again


User currently offlinePW100 From Netherlands, joined Jan 2002, 2509 posts, RR: 12
Reply 8, posted (12 years 1 month 1 week 3 days 18 hours ago) and read 1709 times:

LZ-TLT

Very comprehensive explanation indeed! Just one remark... it's valid only for subsonic flow. At supersonic flow it doesn't work no more. Nature's reaction to supersonic flow is the shockwave.

PW100



Immigration officer: "What's the purpose of your visit to the USA?" Spotter: "Shooting airliners with my Canon!"
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